package org.apache.hadoop.examples;

import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration; 
import org.apache.hadoop.fs.FileSystem; 
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable; 
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; 
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; 
import org.apache.hadoop.util.GenericOptionsParser;

public class WordCount {
	public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable> {
		private final static IntWritable one = new IntWritable(1); 
		private Text word = new Text();
		public void map(Object key, Text value, Context context) 
				throws IOException, InterruptedException {
			StringTokenizer itr = new StringTokenizer(value.toString()); 
			while (itr.hasMoreTokens()) {
				word.set(itr.nextToken()); context.write(word, one);
			}
		}
	}
	
	public static class IntSumReducer extends Reducer<Text,IntWritable,Text,IntWritable> {
		private IntWritable result = new IntWritable();
		public void reduce(Text key, Iterable<IntWritable> values, Context context) 
				throws IOException, InterruptedException {
			int sum = 0;
			for (IntWritable val : values) {
				sum += val.get(); 
			}
			result.set(sum);
			context.write(key, result); 
		}
	}
	
	public static void main(String[] args) throws Exception {
		final String inputPath = "hdfs://localhost:9000/user/hadoop/bbc-tech/";
		final String outputPath = "hdfs://localhost:9000/user/hadoop/lab_0/output/";
		
		args = new String[]{inputPath, outputPath}; 
		Configuration conf = new Configuration();
		conf.set("fs.defaultFS", "hdfs://localhost:9000");
		String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
		if (otherArgs.length != 2) {
			System.err.printf("Args.length = %d : Usage: wordcount <in> <out>", otherArgs.length);
			System.exit(2); 
		}
		Path path =new Path(args[1]); //加载配置文件
		FileSystem fileSystem = path.getFileSystem(conf); //输出目录若存在则删除
		if (fileSystem.exists(new Path(args[1]))) {
			fileSystem.delete(new Path(args[1]),true); 
		}
		Job job = Job.getInstance(conf, "word_count");
		job.setJarByClass(WordCount.class);
		job.setMapperClass(TokenizerMapper.class); 
		job.setCombinerClass(IntSumReducer.class); 
		job.setReducerClass(IntSumReducer.class); 
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(IntWritable.class); 
		
		FileInputFormat.addInputPath(job, new Path(otherArgs[0])); 
		FileOutputFormat.setOutputPath(job, new Path(otherArgs[1])); 
		System.exit(job.waitForCompletion(true) ? 0 : 1);
	}
}